using System;

using System.Linq;

using System.Xml.Linq;

public class Program

{

    public static void Main()

    {

        var doc = XElement.Parse("<Root>" + "abcd<sps>2</sps><sbs>yy</sbs>efgh<sym>b</sym>" + "</Root>");

        var nodes =

            doc.Descendants()

            .Where(e => e.Name == "sps" || e.Name == "sbs")

            .Cast<XNode>()

            .Concat(doc.Nodes().OfType<XText>());

        Console.WriteLine(string.Join("\r\n", nodes));

    }

}